Field of the Invention
The present disclosure relates to content individualization, and more specifically, to individualizing the content using file formatting and encryption.
Background
The Advanced Access Content System (AACS) is a standard for content distribution and digital rights management, intended to restrict access to and copying of the post-DVD generation of optical discs. However, several AACS decryption keys have been extracted from software players and published on the Internet, allowing decryption by unlicensed software.
The AACS sequence key mechanism was developed to provide additional ways to restrict unlicensed use of the content. The sequence key mechanism uses seamless connection and branching with N different segments. The sequence key mechanism first assigns each player a unique set of sequence keys. Discs that use the mechanism contain a special header that a player can decode, using the sequence keys, to get a group of six decryption keys called the variant volume keys. When presented with the same disc, different player often ends up with different variant volume keys. The sequence key mechanism then takes a few clips of the content (e.g., a movie), and puts those clips on the disc several times, encrypted under different variant keys. The content provider creates N slightly different variants of the clips, and encrypts each variant under a different key. Thus, every player knows one of the N variant keys, so it is able to decrypt one of the variants. However, different players decrypt different variants.
The effect of applying the sequence key mechanism is that the content will look slightly different, depending on which player was used to decrypt it. If a ripped copy of the content is redistributed, the central authority can look at which variant of each clip is in the rip, and can then identify which player(s) did the ripping. Having identified a player or players, the authority can then blacklist its keys so the player will be unable to decrypt or play any new discs.